Transformer



Patented June 13, 1939 UNITED STATES PATENT OFFICE 'rnANsmmnPennsylvania Application December 30, 1937, Serial No. 182,483

Claixns.

This invention relates to transformers.

An object of this invention is the provision of the transformer having acore of high magnetic permeability.

Another object of this invention is the provision of a transformer inwhich the core member is free from mechanical stresses and has a highmagnetic permeability.

A further object of this invention is to provide lo a transformer inwhich the coils are rigidly supported by the end frames and the core iscarried l loosely by and between the end frames.

Other objects of this invention will become apparent from the followingdescription when taken 1g in conjunction with the accompanying drawings,

in which:

Figure 1 is a top plan view of a transformer constructed in accordancewith this invention;

Fig. 2 is a side elevational view, partly in secm tion, of thetransformer shown in Fig. l;

Fig. 3 is an end elevational view of the transformer shown in Fig. l;

Fig. 4 is a side elevational view of an end frame employed in accordancewith this invention;

Fig. 5 is an end elevational view of the end frame shown in Fig. 4;

Fig. 6 is a bottom plan view of the end frame shown in Figs. 4 and 5;

Fig. 7 is a plan view of the core member em- 30 ployed in thetransformer shown in Fig. 1;

Fig. 8 is a plan view in elevation of a spacer employed in accordancewith this invention;

Fig. 9 is a side elevational view of another spacer employed inaccordance with this invention;

Flg. 10 is an end elevational view of the spacer shown in Fig. 9;

Fig. 11 is a side elevational view of a channel shaped spacer employedin this invention;

Fig. l2 is a bottom plan view of the channel shaped spacer shown in Fig.ll;

Fig. 13 is a side elevational view of an insert employed in conjunctionwith the channel shaped spacer shown in Fig. 1l;

Fig. 14 is a bottom plan view of the insert shown in Fig. 13; and

Fig. l5 is a plan view of a strip of insulating material employed inthis invention.

Referring to the drawings and Figs. l, 2 and 3 50 in particular, thisinvention is illustrated with reference to a current transformer I0. Thetransformer consists of a core member i2 and a plurality of coils suchas a primary coil i4 and a secondary coil It suitably disposedthereabout. 55 Ihe core and coil assembly is disposed in and suitablysupported in a plurality of end frames il disposed in spaced relation toeach other and maintained spaced as will be explained herein after. Thecore I2 is constructed from a plurality of alternately stacked L-shapedlaminations 2l as illustrated in Fig. 'l which have openings 22 drilledtherein and so spaced as to receive supporting bolts for maintaining thelaminations in their assembled relationsupported between the end frames.

Referring to Figs. 4, 5 and 6, one of the end frames is illustrated indetail. The end frame I8 is fabricated from a single steel sheet memberso cut in one piece as by means of suitable dies orwith a` burning torchinto a substantially rectangular frame having an open end therein forslipping the end frame over the coil assembly and for interrupting themagnetic circuit in the end frame about the coils. In cutting the endframe to shape, an excess of material is left along one edge thereofsuitable for forming a flange 24 when bent inwardly from the plane ofthe frame. In order that the end frame may be seated on a support.sufllcient material, formed to shape, is left so attached to therectangular frame, as by means of the strip of metal 26, that when bentoutwardly it will form a mounting foot 28. Suitable openings II ofdin'erent shapes and sizes may be formed ln the mounting foot forreceiving bolts, etc., to facilitate the mounting of the end frames onany desired support.

The end frames II are. employed in pairs, each of the frames being ofsimilar shape and size and having similarly spaced bolt holes therein,but having flanges 2l and mounting feet 2l extending in oppositedirections when assembled with the core and coil assemblies asillustrated in Figs. 1, 2 and 3. f

In assembling a transformer, the end frames Il are spaced apart adistance slightly larger than the width of any given core assembly andelectrically insulated therefrom by means of strips 3l of suitablematerial inserted between the legs of the core member and the endframes. Thin strips 3l of nbre having a width and length equal to theyoke of the core and bolt holes spaced similarly to the bolt holes inthe core are disposed on both sides of the bottom yoke between thecoreand the end frames to insulate them from the core. The spacing of theend frames is desired in order to prevent any compressive force frombeing exerted on the core by reason Aoi the end frames. In order tomaintain the end frames spaced, a plurality of spacers 32, 34 and 46 areemployed between the end frames about the core. The

spacers 32, 34l and 48 are illustrated in Figs. S, il and 9,respectively, and are of insulating. material such as breboard or sheetsof fibrous material impregnated with condensation resin or wood; formedto a predetermined size to maintain the end frames spaced and the corefree from compressive forces.

As illustrated in Figs. 1, 2 and 3, spacer 32 is disposed between theend frames along the outer leg of the core member and is retained inposition adjacent the leg of the core by the inwardly turned flanges 24of the end frames I8. The spacer 32 is of a length equal to that of theleg of the core and suiiciently Wide to maintain the end frames spacedapart a distance equal to at least the width of the leg or built-upheight of the core member plus thethickness of the insulating strips 3|of bre disposed between the leg of the core and the end frame on eachside of the core.

The spacer 34 is a channel member formed from `fibrous materialimpregnated with condensation resin having a width equal to the width ofspacer member 32 and a length as illustrated in Fig. 3substantiallyequal to the length of the end frame. As illustrated,spacer 34 substantially covers the top of the secondary Winding, the topof the core member, spaces the tops of the end frames and provides asuitable outlet for the leads (not shown) to the secondary coil. Wheninserted between the end frames on top of the core, the side walls ofthe molded spacer extend downwardly adjacent the sides of the -core fora distance equal to the yoke of the core thereby serving to insulate theend frames from the yoke of the core member. Suitable bolt holes 38 and31 and openings 38 for the leads to the secondary coil are drilled intothe side walls of the channel shaped spacer 34 as illustrated in Figs.11 and 12 for receiving assembly bolts and the leads from the coil whenin position with respect to the core and end frames.

In order to strengthen the channel shaped spacer 34, and to furthercover the top of the core, a block 40 of suitable material such as wood,is formed'to shape to t within the channel member 34 when it ispositioned as explained hereinbefore. The insert 40 of wood has aplurality of bolt holes 42 and a grooved out portion 44 as illustratedin Figs. 13 and 14, soformed therein that when inserted in the channelmember 34 the grooved out portion 44 cooperates with the openings 38 inthe spacer to permit the bringing out of the leads from the secondarycoil while the bolt holes 42 are in alinement with the bolt holes 31 inthe spacer.

The core member employed in the illustration is a two-legged core memberdisposed between one end lof the end frames while the other end of theend frames opposite the core end is an open end for permitting the endframe to be slipped over the coils as described hereinbefore.l In orderto aid in supporting and bracing the coils, a spacer 48 of some suitablematerial such as wood and illustrated in Figs. 9 and 10, is employedbetween the end frames to ll the open end thereof. As illustrated, thespacer 48 is of a size comparable to that of a leg of the core an whenpositioned between the end frames gives a symmetrical appearance to theassembled transformer. The top edge of the spacer 46 is recessed on eachside as at 48 to a depth equal to the thickness of the walls of spacer34 to provide for receiving the downwardly extending walls of thechannel member 34. As recessed, the spacer 43 extends upwardly withinthe channel member 34 to a height equal to the top edge of the coremember and aids in supporting the wood block insert 40 within thechannel member 34. Bolt holes 50 are also provided in each end of thespacer 48 for cooperating with the bolt holes formed in the end frame I8for receiving bolts to maintain it in position.

The primary coil I4 and secondary coil I6 are mounted concentricallyabout the inner leg of the core 20 and, in order to support the coilswithout placing the core under supporting stresses, it is necessary tosupport the coils from the end frames I8. As illustrated in Fig. l, thesecondary coil I8 extends beyond or projects through the side of endframes I8 a slight distance. Blocks 52 which project outwardly adistance substantially equal to the exposed portion of the secondarycoil I8 are disposed on and carried by each of the end frames I8 aboveand below the coil to substantially cover the coil I6. In order torigidly attach the coils I4 and I6 to the end frames, a supporting bar54 of fibre is disposed between and projects beyond the primary andsecondary coils to the blocks 52 carried by the end frames and issecured thereto as will be explained hereinafter. The space between theprimary andesecondary coils is filled with a suitable cement such as anasphaltic cement having a high melting point for bonding the coils tothe supporting bar 54 and when the cement is set, it is found that thecoils are rigidly attached to the end frames. In practice the coils arealined in a suitable fixture with the supporting bars 54 in positiontherebetween and hot cement is then poured in between the coils andpermitted to cool and set to rigidly hold the respective elements inposition. A suitable finish coating 55 of tape, a portion of which isshown on the right-hand terminal of Figs. 1 and 2, is applied to theprimary coil before cementing them to give a symmetrical, smoothappearance to the coil assembly extending outwardly to the leads of theprimary coil.

With the core and coil assembly mounted in the end frames disposed inspaced relation by the spacers 32, 34 and 48 as hereinbefore described,the respective elements of the transformer are retained in position bymounting bolts 56 which project through the aligned bolt holes in theassembled end frames I8, in the core assembly, the spacers 34 and 48,the insert 40, the blocks 52 and the fibre strips 54, as will be evidentfrom an examination of Figs. 1, 2 and 3 of the drawings. When tightened,the bolts 58 retain the end frames tightly against the edges of thespacers disposed about the core, but, since the spacers are slightlywider than the core member, the end frames will not exert a compressiveforce on the core member. Where the core member and consequently itslaminations are thus loosely carried by the end frames and do notsupport the coils, it is found that there is an increase in the magneticpermeability of the core member. Such an increase in the magneticpermeability is highly desirable in current transformers.

As a safety feature in conjunction with the transformer describedhereinbeiore, a secondary terminal block 58 is illustrated as beingcarried by one of the end frames I8. Details of the terminal block 58will not be described since any of the well known safety type terminalblocks, such as those illustrated in Patent No. 1,186,746, issuedDecember 30, 1930, to J. B. Gibbs, may be employed in conjunction withthe particular transformer described. This type of terminal blockprovides fixed binding posts for connecting the secondary leads,automatically short circuits the secondary terminals when the cover ofthe block is removed, opens the short circuit when the cover ls replacedin correct position and provides a sealed cover to enclose and protectthe secondary connections.

As is evident from the foregoing description, the transformer of thisinvention comprises a core member carried loosely by the end frames withthe coil members rigidly attached to, and supported by, the end frames.By this construction the core member is free from all compressive forcesresulting from clamping the end frames and is free from stressesencountered in supporting the coil assembly, with the result that anincrease of from 20 to 100% in the magnetic permeability of the core isobtained as compared to that of similar transformers having clampedcores. The spacers employed to maintain the end frames in their spacedrelation with respect to each other for carrying the core member looselytherebetween not only protect the core by relieving pressure therefrom,but, in addition, give a structure having a symmetrical design and afinished appearance.

Although this invention is described with reference to a particularembodiment thereof, it is, of course, not to be limited thereto exceptinsofar as is necessitated by the prior art and the scope of theappended claims.

I claim as my invention:

1. A transformer comprising. in combination, a core member formed from aplurality oi' laminations and having a plurality of legs and upper andlower yoke members, a plurality of coil members disposed about one ofthe legs oi' the core member, a plurality of end frames disposed inspaced relation to each other on opposite sides of the core member, eachof said end frames being a substantially rectangular frame having anopen end therein for slipping the frame over the coil members, means formaintaining the end frames spaced, said means comprising spacer membersbetween the end frames and bolts projecting through the end frames toretain them tightly against the spacer members, certain of the boltsalso functioning to loosely carry the laminations of the core memberbetween the end frames free from compressive forces, the spacer membersbeing of a size suflicient to cooperate with the end frames tosubstantially enclose the upper yoke member and the other leg member ofthe core, and means for rigidly attaching the colt members to the endframes to prevent relative movement therebetween.

2. A transformer comprising, in combination, a core member formed from aplurality of laminations and having a plurality of legs and yokemembers, a plurality of'coil members disposed about one of the legs ofthe core member, a plurality of end frames disposed on opposite sides ofthe core member, each of said end frames being substantially rectangularand having an open end therein for slipping the frame over the coilmembers, the end of each of the end frames opposite the open end beingturned inwardly toward the other end frame when disposed on oppositesides of the core member, a plurality of spacer members disposed betweenthe end frames for maintaining the oppositely disposed end frames inspaced relation to each other, said plurality of spacer memberscompiling a spacer disposed between the inwardly turned ends of the endframes and another of the legs ofthe core member, a second spacerdisposed between the end frames above the upper yoke member of the coremember, and a third spacer disposed between the end frames at the openend thereof, a plurality of bolts projecting through the end frames toretain them tightly against the spacers, certain of the bolts alsofunctioning to loosely carry the laminations of the core between the endframes free from compressive forces, the spacers being of a sizesuilicient to cooperate with the end frames to substantially enclosesaid yoke and leg members of the core to protect them, and means forrigidly attaching the coil members to the end frames to prevent relativemovement therebetween.

3. A transformer comprising, in combination. a plurality of end framesdisposed in spaced relation to each other, means for maintaining the endframes spaced, said means comprising spacer members disposed between theend frames and being of a size suiiicient to substantially close thespace formed between the spaced end frames at their upper and sideedges, a core member formed from a plurality of laminations and havingan upper and lower yoke and a plurality of legs disposed between andcarried by the end frames, the laminations of the core member beingcarried loosely between the end frames. the spacer members and the framemembers cooperating to substantially enclose the upper yoke and at leastone of the legs of the core member, and a plurality of coilsconcentrically disposed about at least another of the legs of the coremember, supporting bars disposed to extend between the concentricallydisposed coils and secured to the end frames, and means for securing thecoils to the supporting bars to prevent relative movement between thecoils and the end frames.

4. A transformer comprising, in combination, a core member formed from aplurality of laminations and having an upper and lower yoke and aplurality of legs, a plurality of coil members disposed about at leastone of the legs of the core member, a plurality of end frames disposedin spaced relation to each other on opposite sides of the core member,each of said end frames being a substantially rectangular frame havingan open end therein for slipping the frame over the coil members, meansfor maintaining the end frames spaced, said means comprising spacermembers between the end frames and bolts pro- ,iecting through the endframes to retain them tightly against the spacer members, certain of thebolts also functioning to loosely carry the laminations of the coremember between the end frames free from compressive forces. the spacermembers being of a size sufllcient to cooperate with the end frames tosubstantially enclose the upper yoke and the legs of the core memberwhich are free of the coils, supporting bars disposed to extend betweenthe coil members and secured to the end frames, and means for securingthe coil members to the supporting bars to prevent relative movementbetween the coils and the end frames.

5. A transformer comprising, in combination, a core member formed from aplurality of laminations and having upper and lower yokes and aplurality of legs, a plurality of coils concentrically disposed about atleast one of the legs of the core member, a plurality of end framesdisposed in spaced relation to each other on opposite sides of the coremember, each of said end frames being substantially rectangular andhaving an open end for slipping it over the coils, means maintaining theend frames spaced, said meansy comprising a plurality of spacer membersdisposed about the core member between the end frames, bolts projectingthrough the end frames to retain them tightly against the spacer memberand in position with respect to the core member, certain of the boltsalso functioning to carry the core member between the end frames, thespacer members being of a size sumcient to cooperate with the end framesto substantially enclose the upper yoke and the legs of the core memberwhich are free oi the coils while maintaining the end frames so spacedthat the core member therebetween is free of compressive forces,supporting bars disposed to extend between the concentrically disposedcoils and secured to the end frames, and means for securing the coils tothe supporting bars to prevent reiative movement between the coils andthe end trames.

EDWARD C. WENTZ.

